Managing Corn Tar Spot: Early Detection and Protection

The presence of tar spot of corn, caused by the fungus Phyllachora maydis, has been confirmed in several fields in Doniphan County, Kansas. To protect crop yields, it is important to increase scouting efforts and take action promptly. Waiting until the disease spreads extensively in the upper canopy may make fungicide applications ineffective.

While tar spot is still being studied in Kansas, experiences from neighboring states show a high risk of yield loss when the disease appears early in the growing season. Recent field observations revealed tar spot lesions on lower leaves, with the potential to spread to the ear leaf and nearby fields. Factors like multiple disease cycles and recent rainfall contribute to tar spot development. Irrigated corn is particularly vulnerable to yield and silage losses.

Farmers should be watchful in scouting for the characteristic symptoms of tar spot, including small black raised spots on leaves, leaf sheaths, and husks. Distinguishing tar spot from insect droppings is important. Seek assistance from local county extension offices or diagnostic clinics to confirm tar spot presence.

Considering the corn's growth stage is crucial for disease management. Research suggests that applying fungicides shortly after initial detection and during or after tassel/silk emergence (VT/R1) is effective.

Timely application is key, as waiting for significant disease progression in the canopy reduces fungicide effectiveness. Regular scouting and monitoring weather conditions are vital, as excessive moisture and high humidity promote disease development.

Choose fungicides with multiple modes of action and assess efficacy ratings for tar spot control. If disease pressure remains high, a second application may be necessary. Monitor tar spot occurrences and contact local experts or diagnostic labs to understand the disease's prevalence.

By remaining attentive, applying fungicides at the right time, and sharing information, farmers can effectively manage tar spot and protect their corn crops from potential yield losses.

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